1. Field of the Invention
The present invention relates to an anode active material for a lithium secondary battery and a lithium secondary battery having the same. More particularly, the present invention relates to an anode active material for a lithium secondary battery, which has large capacity, excellent cycle characteristic and low volume expansion, and a lithium secondary battery having the same.
2. Description of the Related Art
Recently, lithium secondary batteries are attracting attention as batteries having high energy density and a long cycle life. Generally, a lithium secondary battery includes an anode made of carbon material or lithium metal alloy, a cathode made of lithium metal oxide, and an electrolyte made by dissolving a lithium salt in an organic solvent.
Initially, lithium metal was used for the anode active material for the anode of a lithium secondary battery. However, due to lithium having a problem of low reversibility and low safety, generally carbon materials are used as an anode active material of a lithium secondary battery. The carbon material compared with lithium has low capacity, but is advantageous in that it has low volume change, excellent reversibility and low price.
However, as the use of lithium secondary batteries are increasing, so does the demand for high-capacity lithium secondary batteries. Accordingly, there is a demand for a high-capacity anode active material that may substitute the carbon material having low capacity. In order to meet the demand, attempts were made to use metals, for example Si and Sn, that have a higher charge/discharge capacity than the carbonaceous materials and that allow electrochemical alloying with lithium.
However, when Si or Sn are used as the anode active material, they have the tendency to cause great changes in volume expansion. Such great volume expansion may cause the creation of cracks or pulverization. Thus, when charging/discharging cycles are repeated, the metal-based anode active material shows a sudden deterioration of capacity and a shorter cycle life.